June 2016

Construction set to roll again once reservoirs start drying

Delayed by repeated deluges of rain, two dams that for seven decades have prevented $10 billion in property damages – according to the U.S. Army Corps of Engineers (USACE) – are being rehabilitated in a $72 million effort to reduce downstream flooding risk.

The Corps began vital structural renovations in January for Barker Dam and Addicks Dam. While the runoff-full reservoirs have postponed work, the project remains at the front of the Corps’ national priorities, with completion still slated for 2019, according to USACE.

The two dams protect some 1.2 million Houstonians from downstream flooding, the USACE estimates.

The project became a national USACE priority after inspections by the Corps revealed that the dam gates, which control outflow to Buffalo Bayou, and the ends of the dams had potential structural issues. USACE designated both Addicks Dam and Barker Dam with an "extremely high risk" rating in overall flood control. For Houstonians, the classification was a benefit, so to speak, putting the project on the priority list for federal funding.

And the dams have held, despite massive, deadly rainfall events during the past two years.

The Corps began implementing interim risk-abatement solutions in 2009 by replacing the Barker gate and constructing granular filters at the ends of the outlets to add strength, among other measures.

Seven decades of flood control

Flooding has concerned Houstonians since the Allen Brothers set up shop near the confluence of Buffalo Bayou and White Oak Bayou in 1836, naming their “city to be” after San Jacinto battle hero Sam Houston.

Devastating floods drenching downtown Houston during 1929 and 1935 prompted construction of Addicks and Barker dams, and the creation of the Harris County Flood Control District. The now 70-year-old dams were planned to serve for 50 years.

But the original 1940 plan called for more than two dams.

White Oak Bayou had plans for a dam, plus a levee was envisioned for Cypress Creek north of town. Canals were planned. One on the north would ferry floodwater into the San Jacinto River. From the west, another long canal wound south of the city, emptying into Galveston Bay. But those plans never came to fruition.

In a brilliant piece of master-planning foresight as far back as 1913, landscape architect Arthur Coleman Comey – commissioned by the Houston Parks Commission – proposed wide swaths of greenbelts along the bayous, preserving woodland parks that would have served as flood barriers to development (Comey’s Houston plan is available on free on Google Play).

Comey may have appreciated that the Addicks and Barker reservoirs were never excavated. For 90 percent of the year, those reservoirs remain dry – places where outdoor enthusiasts enjoy hiking, bicycling and other activities.

Today, both reservoirs make up two of the largest open spaces next to a major metropolitan area, home to wetlands, creeks, riparian forests, ravines and wildlife.

Terry Hershey Park Trail closed

Rehabilitation construction has also closed the Terry Hershey Park hike and bike trail along Addicks Dam through summer of 2019. Cyclists and walkers can detour off Terry Hershey Park trail just north of IH-10, following the frontage road sidewalk to get to the Addicks Park and Ride and neighborhoods beyond.

“For now, rain and extended pools in the reservoirs has delayed progress, but as soon as things dry out a bit construction will begin again,” said Richard Long, USACE-Galveston District supervisory natural resources manager.

After the work is done, the Corps will re-evaluate the dams' risk rating. USACE is also seeking to study flows from the dams upstream toward areas such as Katy, where development is paving over what was once a huge prairie, full of large “potholes” that held rainfall, serving as wetlands and making the area one of the largest avian migration flyovers in the North America.